1. Field of Invention
The present invention relates to a simple, efficient method of synthesizing 1-chloro-1-iodoethane. More particularly, the process of the present invention comprises the addition of substantially pure and anhydrous hydrogen iodide to vinyl chloride monomer in the presence of an iodine containing catalyst. Under these conditions, the reaction results in 1-chloro-1-iodoethane. 1-Chloro-1-iodoethane is especially effective as a chain transfer agent for the polymerization of vinyl chloride in a process mimicking a living radical polymerization as explained in our co-pending application, referenced above. The 1-chloro-1-iodoethane chain transfer agent formed according to the method of the instant application can be added to a vinyl chloride polymerization system separately after the 1-chloro-1-iodoethane is formed. Alternatively, the 1-chloro-1-iodoethane may be generated in the reaction vessel prior to the polymerization of the vinyl chloride monomer. With the use of 1-chloro-1-iodoethane, a poly(vinyl chloride) polymer having low molecular weight (Mn generally less than 30,000), low polydispersity (generally less than 2.2), and good thermal stability is formed.
2. Description of the Art
The addition of hydrogen iodide to vinyl chloride was first described by Kharasch and Hannum in an article in 1934. The article, entitled "The Peroxide Effect in the Addition of Reagents to Unsaturated Compounds IV. The Addition of Halogen Acids to Vinyl Chloride", J. American Chem. Soc., 56, (1934) p. 712 described the addition of various halogen acids such as hydrogen iodide to vinyl chloride. In particular, Kharasch et. al. discuss the addition of 0.12 moles of hydrogen iodide to 0.1 mole of vinyl chloride in a reactor. By these experiments, Kharasch et. al. were studying the effects of peroxides on reactions which occur via a carbocation process as opposed to a free radical process.
An attempt was made to reproduce the work of Kharasch and Hannum under modern experimental conditions. Using the Kharasch procedure, there was no 1-chloro-1-iodoethane synthesized.
However, applicants have discovered a novel process for synthesizing 1-chloro-1-iodoethane. Accordingly, a primary object of the present invention is to synthesize 1-chloro-1-iodoethane.